Is there anyting we can do in Toronto or nearby on our 4 hour layover? We will probably have about 3 hours to do something. We arrive from Quebec at 4:40 and depart at 8:30.

If you arrive at 4:40 pm during a weekday, then stay at the airport as the rush hour traffic situation will turn a 15 minute ride into one hour.

You can hangout at the end of terminal one which has numerous restaurants and a Starbucks.

If you are set on going somewhere, take a cab to and from the Square One Mall in Mississauga.

Actually, you only have about 1 hour & 45 minutes! If you arrive @ 4:40 by the time you get off the plane, through the airport & out to a cab it will be about 5:15. You shd be back @ PIA by 7:00 for your 8:30 flight, earlier than 7:00 if not domestic. So that leaves you from about 5:15 to 7:00 to leave PIA, get where you are going & back to the airport! And, as Hogtown Jim has pointed out, during the week you will be out there in rush hour traffic which is brutal around the airport. So, I think you shd just roam around the airport. Maybe go over to The Sheraton in Terminal 3 for dinner or just stay where you are for dinner if not in Terminal 3.